Sep 26th, 2009
by Electronics Online.
This is the explanation about “Voltage”
Voltage is commonly used as a short name for electrical potential difference. Its corresponding SI unit is the volt (not italicized). Electric potential is a hypothetically measurable physical dimension, and is denoted by the algebraic variable V (italicized )
The voltage between two (electron) positions “A” and “B”, inside a solid electrical conductor (or inside two electrically-connected, solid electrical conductors), is denoted by (VA − VB). This voltage is the electrical driving force that drives a conventional electric current in the direction A to B. Voltage can be directly measured by an “ideal voltmeter”. Well-constructed, correctly used, real voltmeters approximate very well to ideal voltmeters. For non-scientists, an analogy involving the flow of water is sometimes helpful in understanding the concept of voltage (see below).
Precise modern and historic definitions of voltage exist, but (due to the development of the electron theory of metal conduction in the period 1897 to 1933, and to developments in theoretical surface science from about 1910 to about 1950, particularly the theory of local work function) some older definitions are not now regarded as strictly correct. This is because they neglect the existence of “chemical” effects and surface effects. A particular lesson from surface science is that, to get consistency and universality, formal definitions must relate to positions or (better) electron states inside conductors.
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The Voltage ...
Nov 20th, 2008
by Electronics Online.
In electronics and engineering we often heard something called conductor… what is a conductor..? A conductor is a material which contains movable electric charges. In metallic conductors, such as copper or aluminium, the movable charged particles are electrons (See electrical conduction). Positive charges may also be mobile in the form of atoms in a lattice missing electrons (called “holes”) or ions, such as in the electrolyte of a battery.
All conductors contain electric charges which will move when an electric potential difference (measured in volts) is applied across separate points on the material. This flow of charge (measured in amperes) is what is meant by electric current. In most materials, the rate of current is proportional to the voltage (Ohm’s law,) provided the temperature remains constant and the material remains in the same shape and state. The ratio between the voltage and the current is called the resistance (measured in ohms) of the object between the points where the voltage was applied. The resistance across a standard mass (and shape) of a material at a given temperature is called the resistivity of the material. The inverse of resistance and resistivity is conductance and conductivity. Some good examples of conductors are metal.
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Conductor Explanation ...
Nov 6th, 2008
by Electronics Online.
In this reading we are going to talk about capacitance. I have to make a distinction here between capacitor and capacitance. A capacitor is a device, whereas capacitance is an electrical property. First we will discuss the capacitor and then the property of capacitance.
We will avoid mathematics where possible.
Construction
As you can see a capacitor is a two terminal device. There is always an insulator between the plates of a capacitor. This should suggest to you that current never flows through a capacitor.
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Capacitance Part I ...
Apr 8th, 2008
by Electronics Online.
While you are working on electric circuits, there is often the possibility of receiving an electric shock by touching the “live” conductors when the power is on. The shock is a sudden involuntary contraction of the muscles, with a feeling of pain, caused by current through the body. If severe enough, the shock can be fatal. Safety first, therefore, should always be the rule.
The greatest shock hazard is from high voltage circuits that can supply appreciable amounts of power. The resistance of the human body is also an important factor. If you hold a conducting wire in each hand, the resistance of the body across the conductors is about 10,000 to 50,000 ohms. Holding the conductors tighter lowers the resistance. If you hold only one conductor, your resistance is much higher. It follows that the higher the body resistance, the smaller the current that can flow through you.
A safety rule, therefore, is to work with only one hand if the power is on. Also, keep yourself insulated from earth ground when working on power-line circuits, since one side of the line is usually connected to earth. In addition, the metal chassis of radio and television receivers is often connected to the power line ground. The final and best safety rule is to work on the circuits with the power disconnected if at all possible, and make resistance tests.
Apr 8th, 2008
by Electronics Online.
This article explain the complete basic theory of magneticm.
MAGNETISM AND ELECTRICITY
Any wire carrying a current of electrons is surrounded by an unseen area of force called a magnetic field. For this reason, any study of electricity or electronics must consider magnetism.
Almost everyone has had experiences with magnets or with pocket compasses at one time or another. A magnet attracts pieces of iron but has little affect on practically everything else. Why does it single out the iron? A compass, when laid on a table, swings back and forth, finally coming to rest pointing toward the North Pole of the world. Why does it always point in the same direction?
These and other questions about magnetism have puzzled scientists for hundreds of years. It is only relatively recently that theories seeming to answer many of the perplexing questions that arise when magnetism is investigated have been developed.
Radio and electronic apparatus such as relays, circuit breakers, earphones, loudspeakers, transformers, chokes, magnetron tubes, television tubes, phonograph pickups, tape and disk recorders, microphones, meters, motors, and generators depend on magnetic effects to make them function.
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Magnetism ...
